Stirring deadly civil unrest by cutting off food supplies or energy networks through sabotaging computer systems could bring life sentences.

The British Computer Misuse Act will be amended to include an aggravated offence of unauthorised access to a computer.

The existing offence of impairing a computer only carries a maximum sentence of 10 years' imprisonment.

British ministers believe that punishment does not reflect the potential damage to the British economy and risk to human life posed by an attack by internet terrorists, or a lone hacker working from a bedroom.

Interconnected

The threat has grown as businesses and government become more reliant on interconnected computer networks.

A major cyber attack on essential networks such as the National Grid, police computers or supermarkets' distribution systems could trigger "severe social disruption", the British Home Office fears, according to officials.

Under a Serious Crime Bill, cyber attacks that result in loss of life, serious illness or injury or serious damage to national security will carry a life sentence.